Halfway through 2011, 21 is by far the world's bestselling album, with sales estimated at 8m – and Adele also leads the way in the singles market, with Rolling in the Deep having sold around 6m copies, including more than 4m in the US. The album, her second, deals with heartbreak, and interviewing the 23-year old singer for the Observer in March, Tom Lamont wrote:

"For years Adele's been asked about who she's going out with, who her wounded love songs are about. 'Who cares?' she says. 'Nobody famous, just old boyfriends. I don't date celebrities. I ain't facking Taylor Swift, dyouknowhatimean?' She has an unprintable way of describing a tabloid newspaper when I tell her it recently printed an appeal for information about any boyfriends. She's single, but 'I'd double what the papers pay, anyway. Maybe have someone killed.'"

Adele grew up in London (first north in Tottenham, then south in Lambeth) and enrolled at the Brit School for Performing Arts in Croydon when she was 14.

What we said: "A progressive, grown-up second collection, it ought to ensure Adele is around for 23, 25, 27 and beyond .... The album's highlight, the gorgeous Someone Like You, [is] certain to be coming soon to a montage near you." Will Dean, the Guardian.

Speaking to the Guide in February, 28-year old Calvi said: "When I started recording the album, I thought, 'I'm going to make the most uncommercial music I possibly can'. If it's original in any way, it's because I really didn't care about pleasing anyone other than myself. There was the real possibility that I'd do all the work and no one would ever hear it or like it, but my ambition to make music that makes me happy was stronger than the fear."

Brought up in London, Calvi is a classically trained violinist who taught herself to sing five years ago. After a brief stint in an indie band called Cheap Hotel and a series of early gigs that attracted the attention of Brian Eno, Nick Cave and long-time PJ Harvey collaborator (and eventual producer) Rob Ellis, she signed to Domino and made the BBC's Sound of 2011 longlist.

What we said: "Devils, tick. Desire, tick. Jezebels, check. Even though there is no mention of roses, you know where you are with Calvi – tilting at perdition, red lipstick sharpened. But she can be original, too .... Her debut takes a swirl of familiar tropes and reframes them; it's a gutsy and sonorous start." Kitty Empire, the Observer.

Kathleen Brien grew up in Peckham, south-east London and learned her trade as a vocalist on the underground dance scene. When she was 14, she went to the Brit school for performing arts in Croydon, where she was in the year below Adele and Jessie J, and she finished a degree in popular music at Goldsmiths, University of London last year. Previous ambitions to be an actor, as she told the Guide in in March, were thwarted at an early age: "I auditioned to be Hermione in Harry Potter as well. They were like, 'Have you read the book?' I was like, 'No.' 'Next!'"

What we said: "It isn't being deliberately contrary, or intended as any kind of slight, to suggest the something more Brien has is ordinariness. She's pretty rather than gossip-mag glamorous, and on her debut album she scrupulously avoids the kind of melismatic over-singing that is the female pop star's usual lot in a post-TV talent show world: the inevitable ballad, Go Away, isn't much cop, but at least you can't imagine her doing those I-really-mean-this hand gestures that people do on X Factor. It all fits perfectly with the music she makes, which, almost uniquely for pop music about clubbing, sounds like the work of someone's who's actually been to a club." Alexis Petridis, the Guardian.

Metronomy: The English Riviera

Formed in Totnes in Devon in 1999, Metronomy have released three albums – with The English Riviera inspired by an idealised vision of the south-west. "These LA bands like the Beach Boys and the Eagles: they had so much time," Joe Mount of the band told the Guide in April. "It was just, 'Let's go chill out. Smoke a doob. Spend three months in the studio. Smoke a doob.'" Asked if it was the same in Torbay and Totnes, he replied: "I think it could be. But all it ends up creating is drum'n'bass DJs, tribute acts and singer-songwriter shit. There's another guy from round here who got a record deal recently who does that James Morrison style-thing. That's what it creates: a kind of douchebaggery."

What we said: "The album's title and its music are a homage to [Joe] Mount's native south-west – but it's a sunny, west coastified version, in which cool people drink tequila sunrises and Steely Dan tunes waft out of seafront bars." Caroline Sullivan, the Guardian.

"It's our first record, and we liked the idea of setting ourselves to go off in any direction we please," singer Jonathan Higgs told the Guide in January. "We like the fact that it's like, 'Holy shit, what's going on here?' rather than, 'Oh, they do a particular thing, I wonder if they will do it again, oh yes they will, and there it is again …'"

Everything Everything are based in Manchester, although the four members have origins in Newcastle, Kent and Guernsey. They featured in the BBC's Sound of 2010 and released Man Alive in August 2010, when it debuted at No 17 in the UK charts.

We said: "People might be drawn to Everything Everything for their refusal to sound obvious, but they will stay for this band's mastery of the basics: grooves and feeling." Kitty Empire, the Observer.

King Creosote and Jon Hopkins: Diamond Mine

Writing about this project in March, when we streamed the album, Tim Jonze said: "We've loved King Creosote for a goodly long while now, so imagine our delight when we found out he was teaming up with electronic whizz Jon Hopkins to make Diamond Mine. Featuring old (but unheard) Kenny Anderson songs delivered atop Hopkins's Eno-esque backdrops, this is a project done for the love of it and nothing else. How could you explain a series of songs that have been seven years in the making?" King Creosote is a singer-songwriter from Fife, Scotland, who has has released more than 40 albums to date.

What we said: "It's easy to forget this album is on even while it's actually playing, such is its understatedness .... All is so pastoral that it takes diligent listening to realise Creosote is actually raging – diffidently – about woes such as sibling rivalry and the imprecations of middle age." Caroline Sullivan, the Guardian.

Tinie Tempah: Disc-Overy

Speaking to the Observer in February, the 22-year old rapper described himself as "a soldier for my culture, the voice of my generation". His debut single Pass Out went straight to No 1 in the UK in early 2010 and won best single at the Brit awards this year, where he was also named best breakthrough act. Raised in Plumstead, south-east London, to a family from Nigeria, Patrick Okogwu is now working on a second album, launching a fashion line and aspires to be "a global brand, definitely. I'd like to get past that 'He's just a trend' thing. I want to get to a point where I've consolidated my position in British culture, like Damon Albarn or Chris Martin."

What we said: "For most of Disc-Overy, Tinie Tempah pulls off the not inconsiderable feat of being funny while still suggesting you take him seriously. Despite its flaws, the good bits of the album ... sound like the work of a major talent, who might get better when he realises that he doesn't need to follow trends, that he's at his best when he's being himself, and his producers are making music to match." Alexis Petridis, the Guardian.

James Blake: James Blake

The 23-year-old runner-up in the BBC Sound of 2011 poll grew up in Enfield, north London, the only child of a mother who was a successful graphic designer and a musician father. Making music, he told the Guardian in January, is "something I've done all my life, for purely personal gain". Of his album, which has been compared to the xx's Mercury-winning record of last year, he added: "When I made it I was thinking: 'Is that sound in the right place in the audio field? Those improvisational blips I left in, are they right? Is that space between the two lyrics in Lindesfarne too long?' I was never thinking; 'This is going to sound really good on the radio.'"

What we said: "One thing the world really doesn't need is another straightforward singer-songwriter. It could do with invention and originality, with music that sounds utterly of the moment, in that you struggle to imagine it being made at any point in time before now: precisely the qualities James Blake has, in lieu of commercial potential." Alexis Petridis, the Guardian.

PJ Harvey: Let England Shake

In April, the favourite for this year's Mercury prize told Dorian Lynskey in an interview for the Observer that she was bowled over by the reaction to her eighth studio album. "It's been overwhelming," she said. "People from all walks of life tell me how much it's touched them. It's a wonderful feeling, and not one I'm used to – the feeling that people were hungry for this kind of work." The 41-year-old singer-songwriter, raised in Dorset and Somerset, had parents – a quarryman and a stonemason – who were friends with several musicians. She is a previous winner of the Mercury prize with 2001's Stories from the City, Stories from the Sea.

What we said: "Let England Shake sounds suspiciously like the work of a woman at her creative peak. Where she goes from here is, as ever, anyone's guess." Alexis Petridis, the Guardian.

Elbow: Build a Rocket Boys!

Winners of the Mercury in 2008 ago with The Seldom Seen Kid. Singer Guy Garvey remembered what happened next in an interview with the Observer in February this year: "I was walking down the street and this car slowed and the window wound down. I was semi-expecting something, because it was two days after we'd won ... and this guy just went: 'Oi, Elbow! Get a fucking proper job! Ha ha.'" The band, hailing originally from Ramsbottom in Greater Manchester, have recorded five studio albums.

What we said: "Build a Rocket Boys! makes Elbow's success seem anything but implausible. It may be that people drawn in by One Day Like This hung around because they found music that, while less straightforward, was warm and generous and inventive. If so, they'll find more of it here." Alexis Petridis, the Guardian.

Ghospoet: Peanut Butter Blues and Melancholy Jam

Ghostpoet – aka Obaro Ejimiwe, a London-based Coventry boy with roots in Nigeria and Dominica – was Paul Lester's New Band of the Day No 799 in June last year, and also spoke to the Guardian's Music Weekly podcast team in March this year. Discussing his influences, he singled out The Hour of Bewilderbeast by Badly Drawn Boy, saying: "There are elements in it, the way it's created and put together ... that hit a chord."

What we said: "He sounds like Dizzee on mogadon, or a half-asleep Streets. A lot of his songs are set early in the morning after the night before, and find him doing what might imagine: dreamwalking his way through a series of scenarios, usually quietly nightmarish." Paul Lester, the Guardian.

Interviewing the 30-year-old jazz pianist for the Guardian in January, John Fordham wrote: "If you had to pick a jazz musician – or any other kind of social deviant – out of an identification parade, you almost certainly wouldn't go for the boyish and sprucely groomed Gwilym Simcock. A lot of jazz musicians acquire an air of embattled road-weariness, which they couple with a deadpan Bill Bailey-ish relish for the bleakly ludicrous – but not Simcock. He ... still has a tendency to look at the world around him as if seeing it for the first time."

Born in Wales but raised in Stoke-on-Trent, where his mother Ann left work to home-school him, Simcock studied classical piano, French horn and composition at Chetham's School, Manchester, and then jazz piano at the Royal Academy of Music, London. His playing is often compared to that of Keith Jarrett and he has been called "dazzling" by composer Mark-Anthony Turnage and "a creative genius" by Chick Corea.

What we said: "Unaccompanied piano performance is a challenge 30-year-old Gwilym Simcock hasn't confronted since his childhood classical training, and one that's all the greater because it invites comparison with a significant personal influence: Keith Jarrett. But this highly varied set is more explicitly classical in its harmonic mobility and melodic flourishes and more elaborately composed than Jarrett's jazz work ... [It's] mostly an awesome solo debut." John Fordham, the Guardian.